Hello, I have read a lot of the posts on poly-tunnels, and feel a lot better informed than I was, but still have some doubts about striking out with my own tunnel.
I am a retired farmer so the growing aspects are no problem to me, nor the construction detail. But there is nothing like learning from the experience of others, no matter how much knowledge we may think we have!
I acquired my plot last year and have been slowly 'renovating' the land and getting it back into good heart. The major area I might yet put into green manure with some mustard for rotovating-in. The plot is one of many out in the fields close to a large river estuary, maybe half a mile from the river bank and at about 10 metres above sea level (using GPS). It is on the lower slope of a chalk hill and a nice medium loam with no drainage problems and has a gritty clay subsoil always nicely moist at about 2 ft deep from the surface.
Prevailing wind like most of the country is from the west/south west, but being near the coast we also get the occasional easterly blast too. But poly tunnels are allowed as they reduce the structures with glass panes thus eliminating damage and glass danger.
The plot is east/west, so generally we all grow plants north/south for evenness. It is exposed, although I have a tall hedge on the east about 10 yards from my proposed tunnel site. Looking around the site, I have neighbours with greenhouses but not poly tunnels, though there is a good spread of poly cloches.
Yes, this might sound the alarm for wind damage! But I have a friend who has a poly tunnel on an exposed garden in the fens, though has a hedge maybe 5 metres to the SSW. He has very strong winds to contend with, but has great success with his poly tunnel given that he secures it with a trench with timber planks on top of the film before infilling, he has fence posts inside at each corner, with strong wire connecting them inside of the membrane. He also has wires along the sides between the posts, from bottom of one then gradually rising diagonally to the top of that in the next corner, about 4 ft high. He has hinged doors both ends and no side vents, though says leaving the top half of a door open (netted) gives a nice atmosphere, given that it is not facing the oncoming wind at any time.
My friend also tells me that he has friends who do not trench-in the film, preferring the bottom batten method and legs with fixing plates dug-in about 18 inches under surface. Is one better suited to the wind?
My intention with the plot is to grow high value (i.e. costly for a pensioner to buy at a supermarket) and out of season vegetables. I also raise plants for my wife's cut flower vases in the house.
I have been looking at tunnels and am not impressed by the floppy variety stretched over a weak painted frame often with a zipped/velcro 'door', as sold in quantity by supermarkets and garden centres. My friend also advises against individual side vents too, as they deteriorate very quickly apparently. The green net reinforced film is also wrong I feel. Plants need a full spectrum of colour to photosynthesise correctly.
I expect this to cost a few hundred £'s though am not averse to buying a second hand frame if they are available - but seem scarce. I am looking at a tunnel 20ft long by say, 10 feet wide and over 6ft high. I am also aware that they can cast a shadow over other crops so have to be placed on the northern side of the plot to avoid that problem.
Have I covered everything? My main concern is that I am looking at the right sort of frame, and that whatever it may be, it can be anchored well enough to resist winter winds.
So its best that I ask other users for your valuable experience before I leap! TIA